What Decades Of Primary Polls Tell Us About The 2020 Democratic Presidential Race

Back in April, we put together a three-part series on how well national presidential primary polls conducted in the calendar year before the primary predicted who eventually won a party’s nomination. That analysis covered every competitive nomination contest from 1972 to 2016, and it found that early polls are somewhat predictive of the final outcome, especially when polling averages are adjusted for how well-known a candidate was at the time.

We then applied what we gleaned from 40-plus years of primary polls to all the polls from the first half of 2019, finding that former Vice President Joe Biden had the best chance of winning the nomination. His odds weren’t nearly as good as say, Hillary Clinton’s in 2016, but he was still in the lead. Now, with 2019 behind us, we can analyze surveys from the second half of the year to get an updated look at who might be best positioned to win the Democratic nomination.

Using national polls conducted between July 1 and Dec. 31, 2019, we calculated a polling average for each Democratic candidate — including those who have dropped out — and then adjusted it based on how well-known a candidate was during that period of time (measured on a slightly subjective five-tier scale, which is represented by the black boxes in the table below, where more boxes means higher name recognition).¹ And although his unadjusted average fell slightly from the first half to the second half of the year, Biden continued to lead in the second half of 2019. (Note: This is a different approach than the one our forecast will take when it publishes sometime soon. The polling averages below are not the same as a candidate’s chances of winning, and the forecast will take many more factors into account than this somewhat quick-and-dirty analysis does.)

In fact, Biden’s steady polling average over the year echoes what happened with three previous front-runners: Ronald Reagan in 1979, Bob Dole in 1995 and Al Gore in 1999, all of whom were leading the field in the second half of the calendar year before the election. All three had an unadjusted polling average of 30 percent or more in the first half of the year and were within 3 percentage points of their original number in the second half of the year (Reagan went from 34 to 37 percent; Dole, 46 to 44 percent; Gore, 54 to 55 percent). So the fact that Biden’s polling average has been pretty stable isn’t unprecedented — or even a bad sign. While only Reagan won the general election, all three went on to win their party’s nomination. A fourth candidate, Ted Kennedy in 1979, was in a similar situation the year before the election, and while he fell short of the nomination, it took a sitting president — Jimmy Carter — to block his path. However, those candidates all polled better than Biden — some significantly better — so Biden is by no means a sure bet to win the Democratic nomination, especially as he seems to have experienced a small downturn in the second half of the year, and not an uptick.

But according to our analysis, someone polling around where Biden was in the second half of the year has roughly a 35 percent chance of claiming the Democratic nomination. A 1-in-3 chance isn’t great, but this is still better than, say, Bernie Sanders’s or Elizabeth Warren’s chances. They essentially tied for second, with an unadjusted polling average around 16 percent in the second half of the year, which historically has meant a 10 percent chance of winning.

Former South Bend, Indiana, Mayor Pete Buttigieg has also received top-tier billing in the 2020 primary, but in the second half of 2019, he actually only polled at about 6 percent nationally (without adjusting for name recognition), which historically has translated to roughly a 3 percent shot at winning the nomination. If you’re surprised that his odds aren’t higher, remember that in the first half of 2019, very few people knew who Buttigieg was. He was the only contender with between 20 and 40 percent name recognition to do well enough to have an adjusted polling average in the double digits, but as he has become a better-known quantity in the past few months, his adjusted average hasn’t grown accordingly. It actually dropped from the first half to the second half of the year — despite an uptick in his unadjusted average. In other words, although Buttigieg has become better known, his campaign may not be approaching its ceiling.

Then again, Buttigieg remains less well-known than Biden, Sanders or Warren, so his unadjusted polling average might undersell his chances. After all, he is battling for the lead in Iowa and New Hampshire, two contests that traditionally have had an outsized influence on modern presidential primaries. So Buttigieg’s disproportionate strength in those two states may point to one of the limitations of this analysis.

Early national polls conducted in the year before the first nominating contests do have predictive value, but remember there isn’t one national primary. Instead, parties choose presidential nominees via state-by-state elections over the course of a few months. And that sequential nature of the primary makes it hard for national polls to capture all the dynamics of the race — a candidate falling short of expectations in Iowa or unexpectedly winning both Iowa and New Hampshire can swiftly alter the playing field for the remaining primaries.

But having examined all the national polls from the last six months of 2019, the bottom line is that, at this point, Biden remains the favorite to win the Democratic nomination. That said, his grasp on the lead is tenuous. For instance, when thinking about Biden’s odds, it’s important to remember that the historical data suggests that the rest of the Democratic field combined has a larger chance of winning than Biden does on his own — 44 percent for all of the other candidates still in the race compared with Biden’s 35 percent shot.² And this uncertainty around Biden as the front-runner lines up with what else we know about the race — Biden, Buttigieg and Sanders are fighting for the lead in Iowa while Biden and Sanders are neck-and-neck in New Hampshire, and Biden raised less money than either Sanders or Buttigieg in the final quarter of 2019. So as we jump into the new year and brace ourselves for the first two nominating contests, remember that Biden has the best chance of winning his party’s nomination, but it’s also quite possible that someone else will be facing off against President Trump this November.